From eff722b06bdd6de326894ea2353ec0eda3e5ed34 Mon Sep 17 00:00:00 2001 From: "Srivatsa S. Bhat" Date: Tue, 11 Mar 2014 02:04:45 +0530 Subject: ia64, salinfo: Fix hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the salinfo code in ia64 by using this latter form of callback registration. Cc: Tony Luck Cc: Fenghua Yu Cc: Ingo Molnar Signed-off-by: Srivatsa S. Bhat Signed-off-by: Rafael J. Wysocki --- arch/ia64/kernel/salinfo.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'arch/ia64/kernel/salinfo.c') diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c index 960a396f5929..ee9719eebb1e 100644 --- a/arch/ia64/kernel/salinfo.c +++ b/arch/ia64/kernel/salinfo.c @@ -635,6 +635,8 @@ salinfo_init(void) (void *)salinfo_entries[i].feature); } + cpu_notifier_register_begin(); + for (i = 0; i < ARRAY_SIZE(salinfo_log_name); i++) { data = salinfo_data + i; data->type = i; @@ -669,7 +671,9 @@ salinfo_init(void) salinfo_timer.function = &salinfo_timeout; add_timer(&salinfo_timer); - register_hotcpu_notifier(&salinfo_cpu_notifier); + __register_hotcpu_notifier(&salinfo_cpu_notifier); + + cpu_notifier_register_done(); return 0; } -- cgit